| Electric heating alloy is an electric heating material that transforms electric energy into heat energy by the thermal effect of resistance heating of metal.Its working temperature is up to 1400°C,and it has nearly 10 0%electrothermal conversion efficiency.Therefore,electrothermal alloy processing electrothermal devices In the petrochemical,machinery,petrochemical,electrical,military,construction and other industries a lot of use.However,when Cr20Ni80electrothermal alloy is prepared by general smelting method,carbon can easily form chromium-rich Cr3C2 with chromium,and Cr3C2 is hard and brittle,which affects the alloy processing performance.And it will form a"chromium-depleted layer"near it,reducing the service life of Cr20Ni80 alloy.The theoretical study shows that the adverse effect can only be solved when the carbon content of the Cr20Ni80 alloy is not more than 0.03%.However,the Cr20Ni80 alloy prepared by the conventional smelting method can only control the carbon content at 0.06%,and it is difficult to meet the requirement that the carbon content is less than 0.03%.In the experiment,by adding strong carbonitrides to form elemental Nb,Ti reacts with excess carbon and nitrogen in the alloy to f orm carbonitridine compounds of niobium and titanium,so that carbon is preferentially reacted with niobium or titanium in the metal.Under the carbon can generate and generate chromium carbide,thereby optimizing the organizational stability of the alloy,enhance the use of performance.In this paper,Cr20Ni80 alloys are melted in a vacuum arc furnace and analyzed by optical microscopy?OM?,field emission electron microscopy?SEM?,energy dispersive spectroscopy?EDS?,electron probe?EPMA?,and DC digita l resistance meter systems.Effect of Nb on Microstructure,Mechanical Properties and Resistivity of Cr20Ni80 Alloy.Concluded as follow:?1?After adding Nb or Ti,the grain size of Cr20Ni80 alloy has been refined,and with the increase of the addition am ount,the refinement effect is stronger.Through electron probes,it was found that the precipitates of Nb or Ti were distributed in grain boundaries.?2?Nb or Ti can enhance the tensile strength and yield strength of Cr20Ni80alloy at room temperature.However,as the addition amount increases,the elongation rate of the Cr20Ni80 alloy decreases.The normal temperature tensile fractures of Nb and Ti alloys are macroscopically plastic fractures,and there are a large number of dimples caused by the second phase particles.?3?Nb or Ti can also enhance the high-temperature tensile strength and yield strength of Cr20Ni80 alloy,and reduce the elongation of section.However,under the influence of high temperature,the value is smaller.The high-temperature tensile fractures of alloys with Nb or Ti additions belong to plastic ractures in a macroscopic manner.The fractures have both transgranular fractures and intergranular fractures,and with the increase of the addition amount,the fractures mainly take intergranular fractures.?4?Nb or Ti can increase the electrical resistivity of the alloy,but the increase value is small and the strengthening effect is limited. |
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